<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    table {
      border: 1px solid #000;
      text-align: center;
      width: 300px;
    }
    th,td {
      border: 1px solid #000;
    }
    h3 {
      position: relative;
    }
    span {
      position: absolute;
      left: 130px;
      top: -4px;
      width: 16px;
      height: 16px;
      color: white;
      font-size: 12px;
      text-align: center;
      border-radius: 50%;
      background-color: #e63f32;
    }
  </style>
</head>
<body>
  <div id="app">
    <h3>小黑礼物清单🛒<span>{{ totalCount }}</span></h3>
    <table>
      <tr>
        <th>序号</th>
        <th>名字</th>
        <th>数量</th>
      </tr>
      <tr v-for="(item, index) in list" :key="item.id">
        <td>{{ index + 1 }}</td>
        <td>{{ item.name }}</td>
        <td>{{ item.num }}个</td>
      </tr>
    </table>
     <p>礼物总数: {{ totalCount }} 个</p>
  </div>

  <script src="https://cdn.jsdelivr.net/npm/vue@2.7.16/dist/vue.js"></script>
  <script>
    const app = new Vue({
      el: '#app',
      data: {
        list: [
          { id: 1, name: '篮球', num: 1 },
          { id: 2, name: '玩具', num: 2 },
          { id: 3, name: '铅笔', num: 5 }
        ]
      },
      computed: {
        // 计算属性: 有缓存,一旦计算出来结果,就会立刻缓存
        // 下一次读取 -> 直接读缓存就行
        totalCount() {
          return this.list.reduce((sum, item) => sum + item.num, 0)
        }
      },
      methods: {
        totalCountFn() {
          console.log('methods方法执行了')
          return this.list.reduce((sum, item) => sum + item.num, 0)
        }
      },
    })
  </script>
</body>
</html>